This application claims priority of Japanese Patent Application No. 2001-182112, filed on Jun. 15, 2001.
1. Field of the Invention
The present invention relates to an engine control device. More particularly, the present invention relates to an engine control device for operating an engine, which is originally operated using a predetermined fuel, using another fuel different from the original fuel.
2. Description of the Related Art
Recently, attempts have been made to operate an engine, which is operated using a predetermined fuel, using another fuel different from the original fuel. For example, an attempt has been made to use inexpensive LPG (or CNG) in a gasoline engine. In this case, one engine is provided with two different fuel supply passages where one is a supply passage to supply gasoline and the other is a supply passage to supply LPG. Concerning the computer for controlling the engine, there are provided two different computers, one is a computer to control the engine when gasoline is supplied to the engine as fuel and the other is a computer to control the engine when LPG is supplied to the engine as fuel. Each computer outputs an ignition signal, injection signal and others according to the outputs of various sensors such as an engine speed sensor signal, cylinder signal and others.
As described above, in the case of a conventional engine control device to control an engine which is operated by fuel different from original one, a computer is provided for each fuel, and each computer conducts control under the condition that the objective fuel is used in the engine.
It is an object of the present invention to provide an engine control device, the constitution of which is simple, which is used for an engine to be originally operated using a predetermined fuel, in which the engine is operated using another fuel different from the predetermined one.
The present invention has been accomplished to attain the above object.
An engine control device of the present invention comprises: a main computer for controlling an engine which outputs an ignition signal and injection signal according to an output signal of a sensor on the supposition that a predetermined fuel is used in the engine; and a sub computer for outputting an injection signal according to a signal outputted from the main computer on the supposition that another fuel, different from the predetermined fuel, is used in the engine.
In the engine control device of the present invention, the main computer outputs an ignition signal and injection signal on the supposition that predetermined fuel is used in an engine. The igniter is operated by this ignition signal. The sub computer operates as a computer exclusively used for injection control, that is, the sub computer calculates and outputs an injection signal according to an injection signal or ignition signal outputted from the main computer on the supposition that another fuel, different from the original fuel, is supplied to an engine. The injector operates according to the injection timing and injection amount determined by the injection signal outputted from the sub computer. Ignition control and other control, except for control conducted by the injection signal, are executed by the main computer.
According to the present invention, even when an engine to be operated by predetermined fuel is operated by another fuel different from predetermined fuel, it is possible to conduct injection control appropriate for another fuel, that is, it is possible to obtain injection timing or injection amount appropriate for another fuel. Due to the foregoing, even when another fuel is used, the engine can be operated in the most appropriate condition. Further, engine control, in which another fuel different from the original fuel is used, can be realized by a simple constitution in which a sub computer only for calculating an injection signal is added.
In this connection, in the case where the engine is operated by the original fuel, an injection signal outputted from the main computer may be inputted into the injector.
Concerning the signal outputted from the main computer into the sub computer, it is possible to use an injection signal, ignition signal or ignition coil signal outputted from the main computer on the supposition that predetermined fuel is supplied to the engine. In addition to the signals outputted from the main computer, the sub computer can use a signal outputted from a crank angle sensor.